Material handling apparatus



R. E. BRIGGS MATERIAL HANDLING APPARATUS Aug. 30, 1938.

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MATERIAL HANDLING APPARATUS Filed Dec. 8, 1953 14 Sheets-Sheet 5 VEN TOR Robe/f E 5/1 5 ATT'Y Aug. 3%, 1%. R. E. BRIGGS 2,128,345

MATERIAL HANDLING APPARATUS Filed Dec. 8, 1953 14 Sheets-Sheet e //v vE/v TOR Robehf 5 Br/ 5 BY I ATT'X Aug. 30, 1938. R. E.'BRIGGS MATERIAL HANDLING APPARATUS 14 Sheets-Sheet 7 Filed Dec. 8. 1933 //v VENTOR Robe/"7 557-1 5 BY 79 r A TT'Y Aug. 30, 1938. R. E. amass MATERIAL HANDLING APPARATUS Filed Dec, 8, 1953 14 Sheets$heet 8 [/VVENTOR.

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MATERIAL HANDLING APPARATUS Filed Dec. 8, 1933 14 Sheets-Shet l1 [/v VEN TOR Robe/W -E Br ggs Aug. 30, 1938;

R. E. BRIGGS MATERIAL' HANDLING APPARATUS Filed Dec. 8, 195a 14 SheeCs-Sheet 12 lllll [NI/EN TOR: Robe/f E 5/19 5,

ATT'Y 9 R. E. BRIGGS 2,128,345

MATERIAL HANDLING APPARATUS Filed Dec. 8, 1933 14 Sheets-Sheet 13 f/vvE/v TOR.

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ATT'X 1938- R. E. BRIGGS 2,128,345

MATERIAL HANDLING APPARATUS Filed Dec. 8, 1933 14 Sheets-Sheet 14 Fiq. 2/3

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Patented Aug. 30, 1938 ETED 2;?

MATERIAL HANDLING arraaar'os Robert E. Brig Columbus, Ohio, assignor to The Jefirey Manufacturing Company, a corporation of Ohio Application December 8, 1933, Serial No. 701,548 21 Claims. ((1210-4176) With thegrowth of urbanpopulation and a developing public consciousness of sanitary requirements, the value of sanitary engineers in handling adequately and effectively sewage disposal problems is receiving deserved recognition; and while the science of the chemist and bacteriologist has played andcontinues to play an important part in sanitation, nevertheless, with sewage treatment plants called upon to handle millions of gallons of material daily, the enormity of the task directs attention increasingly toward adoption of mechanical handling methods.

In line with these considerations, the present invention provides an apparatus of the nature of a self-cleaning bar screen which .is designed with the primary purpose of removing solid refuse and trash from a stream of sewage or the like as the latter is passing to the usual settling tanks, so as to efiect removal of such solid material preliminary to the settling operation; but while the apparatus is intended with the primary view of use in connection with sewage disposal operations, it will be apparent that it may be employed "in any operations requiring the screening of solid materials from an accompanying body of liquid. Among the objects of the present invention there may be mentioned specifically that the invention provides a self-cleaning bar screen which provides a clear opening from side to side of the submerged portion, there being eliminated all cross members within the channel to act as obstructions.

A.further object of the invention is to provide a self-cleaning bar screen in which there are no sprockets or shafts at the bottom of the chan--' nel to'require attention, the conveyor chain employed in the apparatus being guided around large radius curves for the return travel of the chain.

A still further object is to provide a hinged rake I or scraper for preventing jamming of the mechanism from accumulation of foreign material in the bottom of the channel or upon the screen.

A still further object of ';the invention is to provide means for gently turning the rake or' scraper from inoperative position into operative position, thereby avoiding'unnecessary shocks or jars to the mechanism.

I A still further object of the invention is to provide a self-cleaning bar screen having return runways for the rakedisposed at a considerable distance from the screen, so that the rake or scraper enters the sewage back of the accumulated refuse and collects any accumulation in front of the screen, coming up under the refuse in suspension.

A still further object of the invention is to provide .a rake or scraper having teeth which pass entirely through the screen, thereby clean- 5 ing not only the surface but also the spaces between the bars, the rake being arranged to pull obstructions out of the screen instead of pushing them through.

A still further object of the invention is to provide wiping mechanism for engaging the rake or scraper after the latter has discharged its load, so that the rake will be freed of any material adhering to it, the wiper being provided with means for automatically returning it to position.

A still further object is to provide control mechanism for operating the rake, the said mechanism including means engageable by the rake for stopping the operation of the apparatus respon-. sively to the rake reaching the upper limit of its return travel, and mechanism for automatically re-starting the apparatus after a predetermined time interval, instrumentalities being also provided for operating the control mechanism continuously as well as at predetermined intervals.

A still further object of the invention is to provide means for releasing the mechanism without damage, should some unusual obstruction be encountered.

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings, and described in the following specification, and it is more particularly pointed out in the appended claims.

In the drawings:

Fig. l is a perspective view of one form of apparatus embodying the principles of the present invention;

Fig. 2 is a fragmentary front elevation of the upper part of the apparatus, the view showing 40 the driving mechanism therefor;

Fig. 3 is a side elevation of the parts shown in Fig. 2;

Fig. 4 is a fragmentary sectional elevation showing the lower part of the screen and track for the conveyor chain, the mounting of the rake or scraper upon the chain, and means for easing the rake from inoperative position into operative position, the rake or scraper being shown in section;

Fig, 5 is a plan view of the lower end of the screen, the chain and scraper mechanism of Fig. 4 being omitted, the view being taken on line 55 of Fig. 4;

Fig. ,6 is a front elevation of the entire screen, 65

includingthe tracks or guides for the conveyor chain carrying the rake or scraper, the view being taken looking in the direction of the arrows Fig. 7 is a sectional elevation through the entire apparatus, the view being along the longitudinal axis of the apparatus;

Fig. 8 is a transverse sectional view through the screen and conveyor tracks, the view showing the position of the rake or scraper relative to the screen when in operative position;

Fig. 9 is a sectional view on the line 9-9 of Fig. 8;

Fig. 10 is a view similar to Fig. '7, but showing .a somewhat modified form of apparatus;

Fig 11 is an enlarged side elevation of the upper part of the structure of Fig. 10, the view illustrating certain of the drive mechanism for the apparatus the View also showing, in trans verse section, a conveying device for receiving and removing material discharged from the screen by the rake or scraper;

Fig. 12 is an elevational view, partly in section, of the screen of the apparatus of Fig. 10, showing details of mounting of the screen;

Fig. 13 is a section on line |3-|3 of Fig. 12;

Fig. 14 is a fragmentary elevation of the lower part of the screen and guides for the conveyor chains of the apparatus of Fig. 10, showing a provision of means for lifting the guides;

Fig. 15 is a section taken on line |5-|5 of Fig. 14;

Fig. 16 is a fragmentary sectional view taken on line |6-|6 of Fig. 11;

Fig. 17 is a sectional view of Fig. 11;

Fig. 18 is a wiring diagram of the control mechanism for operating the apparatus;

Fig. 19 is a side elevation of the apparatus installed in a vertical position; 1

Fig. 20 is a fragmentary plan view of the rake or scraper employed in the installation of Fig. 19, showing means provided for maintaining the rake or scraper in engagement with the vertically disposed bar screen;

Fig. 21 is a fragmentary side view of the mounting of the rake of Fig. 20;

Fig. 22 is a side elevation of the screen, illustrating the screen as being provided with a grit removing attachment; n

Fig. 23 is a fragmentary side view of the flower end of the apparatus of Fig. 22, illustrating the grit remover in operative position.

Referring more particularly to the drawings, the apparatus embraces essentially a screen A, adapted to be submerged in a tank or pit into which the liquid, such as sewage, to be screened is being passed, guide tracks B for the chains carrying the rake or scraper C, and the supporting framework D, which supports the upper part of the screen and guide tracks and also carries the drive mechanism for operating 'the chains and scraper. It will be observed that the screen comprises a plurality of spaced bars I, equi distantly spaced relatively to the angle bar 2 and bottom plate 3, the plate 3 having the bars I welded thereto, and thus maintainingthe bars I in proper spaced relation. The Width of the screen A may be whatever is desired for any given installation, being sufiicient to extend across the width of a tank or pit 4 inwhich the screen A is submerged. The upper ends of bars I terminate adjacent a curved plate 5 as will be apparent from Fig. 3, for example, and are welded thereto.

To the ends of angle bars 2 are secured upright angle standards 6 and 1, the upper ends of which are connected by the horizontal angle 8 and braced by plates 9, 9 riveted, bolted or welded to the upright and horizontal members. Also from each end of the angle 2 extending rearwardly thereof, are the horizontal angles l0 and ll, the ends of which are connected by an angle bar 2a corresponding to the angle 2. Upright angle bars i2 and I3 are secured to the bars ill and H, these bars corresponding to the bars 6 and and are of equal length therewith, these bars l2 and i3 being braced by similar plates, one of which is indicated at M.

The supporting framework D is completed by the horizontal bars l5, l6 and rear plate IH, the latter being secured to an angle bar l'la.

Extending horizontally between the Vertical standards 6 and i2, and I and I3, are corresponding horizontal angle beams is and I9, suitably braced by plates 26 and 2| secured to the rear uprights, |2 and i3. Diagonal braces 22, 23, 24 and 25 further strengthen the framework D, these braces being secured to the brace plates 20 and 2| and also to brace plates'26, 21, 28 and 29, as will be apparent from the drawings.

Positioned above the bars I of the screen A are the guide tracks B for the endless flexible chains 30 and 3| to which the scraper or rake spectively, and being anchored by bolts 32a to 4 the sides of the pit 4. I

The chains 30 and 3| are made up of links 34 pivotally interconnected by horizontal pivot pins 35 so that the chains will be freely flexible in a vertical direction. To corresponding links 34 of the chains 30 and 3| are bolted corresponding plates 36 and 31 to each of which plates is hingedly secured at 38, an arm 39, each of which arms is provided with a flange 40, to which plates is bolted as indicated by bolts 4|, the angle member 42 which connects the arms 39. The scraper or rake C is welded to the angle member 42.

The rake C comprises a b0dy43, the ends of which are formed into shoulders 44 which engagethe top angles 32 of the guide tracks B during the downward travel of the scraper. The scraper is provided with teeth 45 which are adapted to pass between the bars I of the screen when the rake assumes its operative position, the teeth 45 passing entirely through the screen A.

It will be noted from chains 30 and 3| travel around large radius curves 46 in their guide tracks for the return run of the chains. As the chains approach these curves, it will be seen that the teeth 45 of the rake C extend upwardly, the arms 39 resting upon pins 41 extending through the plates 36 intermediate the members 48 securing the plates to the chains. In order for the rake C to assume its operating position with its teeth 45 extending between the bars I, it will be apparent that the arms 39 must swing through an arc of approximately or until they engage other pins 49 in the plates 36 which pins 49 are provided for supporting the rake in its operative position.

Because of the substantial weight of the rake,

the drawings that the transposition of the arm 39 from the pins 41 to the pins 49, as aforesaid, the shoulders 44, 44, sliding along the cam surfaces of the members 59 in continuous engagement therewith as the rake assumes its operative position incident to the conveyor chains passing around the bends 46 of their tracks.

It will be understood that the screen A is installed in its pit or tank so that the flow of liquid is against the upper surface of the screen, the bars 1 thereof catching and retaining solid matter carried by the liquid current. It will be apparent that such solids will accumulate in front of the screen to a greater or less extent, depending upon the time intervals between the operation of the rake. It will be seen further that the curved portions-46 of the tracks project sumciently far forwardly of the end of the screen to enable the rake C, as it turns into its operative position, to enter the liquid back of the accumu lated solids, thereby collecting the accumulation in front of the screen, and coming up under the refuse in suspension; and since the teeth 45 of the rake extend entirely through the interstices between the bars I as the rake travels upwardly along the screen, it will pull any obstructions out of the screen instead of pushing them through.

In order to maintain the bars I in equi-spaced relation throughout their entire length during all operating conditions, one or more brace bars5| may be provided extending transversely of the screen A, being welded to the extensions 52 of the bars I, so that the brace bars 5| will be spaced sufficiently far below the screen to enable the teeth 45 to clear these brace bars.

To protect the bottom of the pit or tank in which the screen is installed from. the scraping action of .the rake and to maintain the bars I in proper spaced relation, the plate 3 is embedded in the concrete of the pit, as at 53, and anchored by means of, anchor members 54. The solid refuse accumulates on this plate and the teeth 45 scrape the surface of the plate as it gathers the accumulation: Lateral guide plates 55 may be provided for guiding the rake upon the screen.

When the rake reaches the top of the screen A, it pushes the collected refuse onto the plate 5,

whence the refuse is discharged on suitable coirveying instrumentalities 56 for conveying it away to disposal. As the material discharges from the plate 5 onto conveyor 56 (Fig. 3), the rake engages wiping mechanism including a wiper 51 mounted on arms 58, 58 of bell cranks 59, 59 which are pivoted at their fulcrums 69, 69 to the shaft 69a extending past the standards or bars l5 and I6 of the framework D, the bars I5 and I6 being provided with bearing? 6|a, 6|a in which shaft 69a turns. The arms 6|, 6| of the bell cranks 59, 59 are provided with counter-weights 82, 62, and are resiliently cushioned on springs 63, 63 carried by bolts 64, 64 mountedon angle bar 65. Engagement of the rake with the wiper 51 depresses the arms 58, 58 of the bell cranks 59, 59, raising the arms 6|,- 6| as indicated by dotted lines in Fig. 3, for example. When the rake has passed over the wiper 51, the weights 62, 62, return the bell-cranks 59, 59 to their former. position.

Coming now to a consideration of the drive mechanism for the chains 39 and 3|, it will be observed that the chains are guided throughout substantially their entire length by the guide tracks B. These guides B terminate, however, just short of the sprockets 66, 66 connected by a head shaft 61 mounted in suitable bearings 68,

68 on take-up frames 68a, 68a mounted on the f horizontal brace angles l8 and i9 of the framework D. The sprockets 68, 66 drive the chains 39 and 3|, the shaft 61 being in turn operated by a drive sprocket 69 operated by a sprocket chain it, driven by sprocket ll. Sprocket ii is mounted on a drive shaft 12 of a standard type of speed reducer l3, operated in turn by a motor l4. As the rake clears the wiper, the body 42 of the rake engages a roller 75 (Fig. 2) mounted on an arm E6 of a limit switch 11 carried on the channel 'l'la supported at one end by the shaft 61, the other end of the channel being supported on the horizontal angle 66a, the limit switch I? thereby being tripped and the motor 14, being controlled by the limit switch, is stopped until the circuit is re-made upon expiration of the period for which the timingv means in circuit with the limit switch'is set, when the motor i4 and drive mechanism for the rake will be re-started to resume operation of the rake.

may be conveniently a dash pot.

As a matter of fact, the'rake may be continuously operated, if desired. Fig. 18 illustrates the details of the wiring of the. controls for the operating mechanism. It will be seen that the power is taken from a. three-phase line indicated on Fig. 18 by conductors L1, L2, L3. For continuously operating the rake, a-hand switch is.

provided which maintains continuous the circuit through the motor, and for the intermittent operation of the rake, a second switch is provided operable simultaneously with, but in opposition to, the first mentioned switch, for controlling certain timing means as will be explained hereafter.

Therefore, when it is desired to continuously operate the rake, the switch, indicated at 18, Fig. 18, is closed, the switch 18a being opened.

Now, when the switch 18 is closed, a circuit will be established from L1 of the main line through conductor 19, thence through the switch 18, conductor 99, magnetic coil 8|, conductor 82, thermal safety cut-out 83, conductor 84, to the main line conductor L3. The coil 8| becoming ener'gized, it pulls up the plunger 84a to close the motor control switch 85, thereby establishing a circuit through the motor 14. The motor 14 will thus be operated continuously until the hand switch 18 is opened, and consequently, therake will be operated continuously.

When periodic operation of the rake is desired,

the switch 18a is closed, and the switch 18 is The limit switch is of standard type and the timing mean gization of the coil I04 and engagement of the contact 93 on the rod 9| with contact 94, which is driven, and the operation of the rake continues.

until it comes into contact with the roller I5 mounted at the end of the limit switch operating lever I6. Engagement of the rake C with roller I5 rocks the lever I6 about its pivot IIII, thereby pulling rod 98 against the pressure of the spring I I4, thus compressing the spring and opening the normally closed contacts I02 and I03 and closing the contacts I I I and I I2. Thisaction is such, however, that contacts 02 and I03 do not open until after contacts III and 2 are closed, so that a holding circuit is maintained through contacts II and H2 and motor I4 so as to assure the rake being operated sufficiently long to pass the roller I5.

Engagement between rake C and roller I5 and consequent operation of the lever I6 trips the limit switch, and opening of the contacts I02 and I03 de-energizes coil I04, allowing the piston I00 of the dash pot to drop. When, due to the action of the holding circuit as above mentioned, the rake C has passed by the roller 15, the spring H4 is released, thereby moving rod 98 in .the

. opposite direction to close the normally closed contacts I02 and I03, thereby again starting the lifting of the dash pot piston I00 and opening contacts III and M2 to break the holding circult, thereby stopping the motor and the rake, thesebeing rendered inoperative until the time required for the plunger rod 9| to be lifted to again, close the contacts 93 and 94, the speed of operation of the dash pot being closely controllable by suitably adjusting, as desired, a'pet-cock, or the like, 99 which controls the flow of air into the dash pot. Air is permitted to pass through the piston I00 of the dash pot by way of a valve |0| therein, the valve opening as the piston drops,

contact with roller I5 and prevent contacts I02 and I03 from closing, thereby holding the timing circuit open, thereby interfering with the automatic operation of the system.

As the roller I5 is freed from the rake, the

- spring I I4 acts to close the normally closed contacts I02 and I03 and open the normally open contacts I II and and II2, thereby re-establishing the circuit through the timing mechanism which will begin to re-time for the next starting of the conveyor motor I4.

The form of apparatus described up to this point is fixedly secured in the pit or tank. It may be convenient, however, to movably mount the screen and guide tracks relative to the pit or tank to render access to the interior thereof more convenient, and to render the apparatus itself more available for repair or replacement of parts. This modification is illus rated'in Figs. 10 to 17, inclusive, in which views parts corresponding to the parts of the apparatus of Figs. 1 to 9 inclusive are designated by like reference characters.

In this modified form, both the screen A and guide tracks B are hingedly mounted at their upper ends so that they maybe swung, in a vertical plane, clear of the pit or tank in which the screen is submerged, as indicated by lines I32 and I3I, in Fig. 10. The hinged mounting of the tracks B enable them to be raised independently of the screen A, thus affording convenient access to the screen, which, in turn, may then be lifted if desired.

To this end, the supporting framework D is provided with horizontal braced brackets H5, H5, having bearings I I6, H6 thereon, in which bearings are mounted a shaft II'I to which the plate 5 is secured; and, as previously described, the plate 5 is welded to the screen A. The shaft II! and bearings H6, H6 afford the hinged mounting for the screen A. For supporting the screen A, dicated at IIB, these notches fitting over bars or rods II9 embedded in the concrete of the pit and desirably, for strength, extendingfrom side to side through the pit, transversely of the screen, to support the latter across its entire width; or, if desired, these rods may extend from each side of the pit only sufficiently far to enable the side bars of the screen to rest thereon. As before described, the screen may be provided with one or more transversely extending bars 5| for properly spacing and bracing the bars I of the screen. Obviously, the rods 9 and bars 5| must be sufficiently below the path of travel of the rake teeth 45 to enable these teeth to freely clear the bars, so that the pathof travel of the rake will be continuously unobstructed. The bars 5| make convenient means enabling suitable hoisting mechanism to be attached to the screen for lifting it. The guides B are notched as indicated at 8', for support on a rod H9, similar to rods H9.

As will be seen very clearly from Fig. 10, the

the bars I thereof are notched as inguide tracks B may also be lifted. For this pur-\ pose, the upper and lower members 32 and 33 of the tracks are extended behind the shaft 61,.

and .are interconnected by the angle bars I20, I2I, to which plates I22, I22, (see Fig. '11, for example) are secured. vThe plates I22 are provided with elongated slots I23, through which slots the shaft 61 is passed. It will be seen, therefore, that the guide tracks B are hingedly mounted on the shaft 61.

In order to enable the guide tracks B to be lifted conveniently, and to brace the forward and return runs of the conveyor chains, there may ,be provided the braces illustrated in Figs. 14 and 15, wherein the forward and return runs of the guide tracks, are interconnected" by brace channels 24, I24 welded to the guide tracks out of the path of travel of the rake. The channels I24, I24 are interconnected by cross-beam I25, I25, braced by brackets I26, I26 welded to channels I24, I24 and to the beam I25. Between this beam I 25 is secured a plate I21 havingan opening I28 thereinto receive a suitable lifting tool; and while the path of travel of the rake-is wholly unobstructed, it will be seen that the entire screen structure is rigidly braced.

Because of the complete penetration of the interstices between the screen bars I by the teeth 95 of the rake,.in both forms of the apparatus, the screen is self-cleaning and the movement of the rake is such that obstructions will be pulled out of the screen instead of being pushed through the screen; this action is facilitated by the hinged mounting of the rake, which hinged mounting also prevents jamming of the mechanism from accumulations of foreign material in the bottom of the channel or upon the screen. However, in the event that some unusual obstruction be encountered by the rake to cause the rake to jam, it is desirable to provide means for releasing the mechanism without damage.

This is accomplished through the provision of one or more shear pins I29 connecting the sprocket 99 with the shaft 61, so that if undue strains are imparted to the mechanism, the pins I29 will shear off, allowing sprocket 69 to freely rotate. replaceable, and form yieldable connections between the driving sprocket 69 and head shaft 61.

It will be understood, of curse,-that except for the differences in structure incident to the hinged mounting of the screen and guide tracks in the second form of the apparatus described above, the construction is the same in both forms, both mechanically and electrically, and the operation of the rake is identically the same in both cases.

It will be observed that bars I39 are provided on each upper .corner of plate 5,.these bars sloping downwardly to prevent too forceful dropping of the rake C when the rake clears plate 5, it being understood that bars I39 are engaged by the rake just before the rake changes its direction of travel.

Referring to Figs. 19, 20 and 21, it will be seen that the screen A is installed in a vertical position, which requires the provision of means for maintaining the rake or scraper C in operative engagement with the bars I of the screen. For this purpose, there may be provided a spring I33 adapted to press against each arm 39 of the rake C, the springs I33 being of sufficient strength to overcome the weight of the rake and to maintain a firm engagement between the rake and screen. For mounting the spring, each of the plates 36 is provided with an additional pin I34 around which the spring I33 is twisted, and which forms a fulcrum about which the spring operates. One end of the spring is bent around the pins 91 for anchorage. In this manner, there are provided yieldable mountings for the scraper, which maintain the rake in proper operative engagement with the screen.

The installation represented in Figs. 22 and 23 shows a bucket I35 mounted on the chains 30 in advance of the rake C, for the purpose of removing heavy materials such as sand, cinders, gravel, etc., which may be associated with the incoming sewage. For collecting such materials a sump I36 may be provided at the bottom end of the screen and the bucket I36 is adapted to enter the sump, as shown in Fig. 23 and scrapes out the materials accumulated therein. The bucket I36 is mounted like the rake C. Plates. I37 are like plates 36, arms I38 carrying the bucket I35 are like arms 39 carrying the rake,

from operative to inoperative positions and con- I trarily, are like the corresponding movements of These shear pins are of course readily MI against which plate the bucket I35 scrapes.

The bucket I35 enters the material accumulated in the sump from behind the material, and effectively removes it.

In the installations shown in Figs. 19 and 22, the collected materials may be dumped in a hopper I 52, communicating with a suitable collecting receptacle I93.

Referring further to Figs. 11 and 1'7, it will be seen that the shaft 91 is journalled in plates I44, I99, through bearings I95, I65, these bearings being provided with bushings I95, I96. The plates I39 are also provided with slots MI in addition to the slots I23, previously referred to, the bearingsIdS being secured in these slots by bolts I95,

I48, and I99, I49, release of which bolts enables the shaft 61 to be moved along the slots I23, thus forming a slack take-up for the chains 39. The mechanism for moving the shaft comprises the screws I59, I59, passing through bearings I5I, I5I, provided with lugs I52, I52. and I53. I53. between which lugs are positioned nuts I58, I58, threaded on the screws I59. These screws are supported in angle bearings I57, I5I, on the beams I8 and I9. The members I5I are parts of the trunnion take-up bearings I55, I55. Adjustment of each screw by the respective head I54 causes relative travel of the nuts I58, producing corresponding movement of thebearlngs I55, I55, which bearings are located adjacent the ends of the shaft 6?. These bearings may be provided with bushings I56, I56, in which the shaft rotates. adjusted for the length of the slots I23, for taking up slack in the chains 39, and may be secured in position by tightening the bolts I48, angles I59 on the angle beams I9 and I8, respectively, form guide tracks along which the take-up bearings I55 move. Nuts I69 are provided at the end of the screws I59 to prevent displacement of the screws, the nuts being held against rotation by suitable means, such as a cotter-pin, not shown. The construction of this take-up bearing is substantially similar to that shown in the United States Patent No, 1,837,260, granted December 22, 1931, to Earle V. Francis. J

In Figs. 1 and 3, it will be noted that there is provided a sprocket I6I mounted on shaft I62 for the purpose of tightening the chain '19, while in Figs. 19 and 22, a somewhat different form of take-up is shown. In these last-mentioned views, the upright standards I63, of which there are two, but only one shown on the drawings, are provided with, a telescoping end section I64 provided with slots I65, I65, through each of which extends a limit pin I66 and H51, respectively. A

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I wish therefore not to be restricted to the precise construction herein disclosed. Having thus described and shown an embodi- The shaft 61 may therefore be ment of my invention, what.I desire to secure by Letters Patent of the United States is:

1. A screening apparatus comprising the combination with a screen portion, of a rake or scraper adapted to pass over the screen, a bucket operating over the screen in advance of the rake, mechanism for moving the rake and bucket along the screen, and hinged mountings for the rake and bucket for enabling the rake and bucket to assume operative positions upon passing a predetermined position relative to the screen, the said bucket being adapted to enter a sump adjacent the bottom of the screen and to collect therefrom granular material collected in the sump.

2. In a liquid screening apparatus, the combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof, of a pair of endless draft means positioned adjacent the edges of said screen adjacent the upstream side thereof, spaced stop means on each of said draft means, a pivoted rake carried between said draft means and adapted to move pivotally between said stops, said rake resting against one of said stops during the downward travel of said rake and being adapted to move from said stop toward the other stop as said rake approaches its lowermost position, and means for lifting said rake from said first mentioned stop as said rake approaches said lower--' of guide means adjacent the upstream side ofv said screen comprising a pair of U-shaped guide tracks, a pivoted rake adapted to pivotabout its axis at is passes around the bottom of said guide tracks, means adapted to move said rake along said guide tracks and across said screen, stop means for supporting said rake above its pivot during downward travel thereof, and cam means adaptedto liftsaid rake away from said stop means as said rake approaches the bottom of said guide tracks.

4. In a liquid screening apparatusthe combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof, of guide means adjacent the upstream side of said screen comprising a pair of U-shaped guide tracks, a pivoted rake adapted to pivot about its axis as it passes around the bottom of said guide tracks, means adapted to move said rake along said guide tracks and across said screen, stop means for supporting said rake above its pivot during downward travel thereof, and cam means adapted to lift said rake away from said stop means as said rake approches the bottom of said guide tracks said cam means being'carried by said guide means.

-5. In a liquid screening apparatus, the combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof, of draft means adjacent the upstream side of said screen and adjacent the side thereof, said means being arcuate adjacent the bottom of the screen, a pivoted rake carried by said draft means, stop lugs carried by at least one of said draft means between which said rake can pivot, said rake being adapted to rest on one of said stop lugs during the first part of its downward travel and against another of said lugs during the last part thereof, and cam means adaptedto move said rake from said first mentioned stop lug toward the other stop lug as the rake approaches the bottom of its travel. 7

6. In a liquid screening apparatus, the combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof,

of guide means adjacent the upstream side of said screen and adjacent the sides thereof, said means being arcuate adjacent the bottom thereof, a pivoted rake extending between said guide means, draft means for moving said rake with respect to said guide means and across said screen, a pair of stops between which said rake is pivotally movable, said rake resting on one of said stops during the first part of its downward movement and against the other of said stops during the last part thereof, and cam means carried on said guide means adapted to move said rake from said first mentioned stop toward said second mentioned stop as the rake approaches the bottom of said guide means.

7. In a liquid screening apparatus, the combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof, of a pair of U-shaped guide tracks adjacent the upstream side of said screen and positioned one adjacent each edge thereof, said guide means comprising substantially parallel side walls, endless draft means carried by said guide means between said side wall, means for driving said draft means, oppositely positioned plates carried by said draft means, at least one of said plates carrying a pair of stop lugs, a rake pivotally connected to said plates and adapted for pivotal movement between said stop lugs, said rake normally resting on one of said lugs during its downward travel, and cam means carried by said guide means adapted to move said rake from said one stop lug toward said other stop lug as said rake approaches the lower end of said guide means.

8. In a liquid screening apparatus, the combination with a screen adapted to extend into a refuse laden stream to catch the refuse thereof,

of a pair of U-shaped guide tracks adjacent the upstream side of said screen and positioned one 'adjacent each edge thereof, said guide means comprising substantially parallel side walls, endless draft means carried by said guide means between said side wall, means for driving said draft means, oppositely positioned plates carried by said draft means, at least one of said plates carrying a pair of stop lugs, a rake pivotally connected to said plates and adapted for pivotal movement between said stop lugs, said rake normally resting on one of said lugs during its downward travel, and cam means adapted to move said rake from said one'stop lug toward said other stop lug as said rake approaches the lower end of said guide means.

9. In a liquid screening apparatus, the combination with a stationaryscreen adapted to extend into a refuse laden stream and to catch the refuse thereof, of a rake to clean said screen, a pair of endless draft chains mounted on sprockets above said screen and extending into said stream along the edges of said screen, stationary U-shaped means adjacent the lower part of said screen providing the sole lower guide and supporting means defining the lower track of said chains,

means attaching the ends of said rake to said adjacent the top thereof, and a rake lifting cam carried by said guide track.

11. A guide track for a sewage screening apparatus chain comprising a pair of parallel plates 

